Short-term muscle disuse induces a rapid and sustained decline in daily myofibrillar protein synthesis rates

Sean P. Kilroe, Jonathan Fulford, Andrew M. Holwerda, Sarah R. Jackman, Benjamin P. Lee, Annemie P. Gijsen, Luc J. C. van Loon, Benjamin T. Wall*

*Corresponding author for this work

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Abstract

Short-term muscle disuse has been reported to lower both postabsorptive and postprandial myofibrillar protein synthesis rates. This study assessed the impact of disuse on daily myofibrillar protein synthesis rates following short-term (2 and 7 days) muscle disuse under free living conditions. Thirteen healthy young men (age: 20 +/- 1 yr; BMI: 23 +/- 1 kg/m(-2)) underwent 7 days of unilateral leg immobilization via a knee brace, with the nonimmobilized leg acting as a control. Four days before immobilization participants ingested 400 mL of 70% deuterated water, with 50-mL doses consumed daily thereafter. Upper leg bilateral MRI scans and muscle biopsies were collected before and after 2 and 7 days of immobilization to determine quadriceps volume and daily myofibrillar protein synthesis rates. Immobilization reduced quadriceps volume in the immobilized leg by 1.7 +/- 0.3 and 6.7 +/- 0.6% after 2 and 7 days, respectively, with no changes in the control leg. Over the 1-wk immobilization period, myofibrillar protein synthesis rates were 36 +/- 4% lower in the immobilized (0.81 +/- 0.04%/day) compared with the control (1.26 +/- 0.04%/day) leg (P <0.001). Myofibrillar protein synthesis rates in the control leg did not change over time (P = 0.775), but in the immobilized leg they were numerically lower during the 0- to 2-day period (16 +/- 6%, 1.11 +/- 0.09%/day, P = 0.153) and were significantly lower during the 2- to 7-day period (44 +/- 5%, 0.70 +/- 0.06%/day, P <0.001) when compared with the control leg. We conclude that 1 wk of muscle disuse induces a rapid and sustained decline in daily myofibrillar protein synthesis rates in healthy young men.

Original languageEnglish
Pages (from-to)E117-E130
Number of pages14
JournalAmerican Journal of Physiology : Endocrinology and Metabolism
Volume318
Issue number2
DOIs
Publication statusPublished - Feb 2020

Keywords

  • atrophy
  • disuse
  • immobilization
  • muscle protein synthesis rates
  • skeletal muscle
  • HUMAN QUADRICEPS MUSCLE
  • SKELETAL-MUSCLE
  • IN-VIVO
  • BED REST
  • ELECTRICAL-STIMULATION
  • ANABOLIC RESISTANCE
  • ATROPHY
  • EXERCISE
  • IMMOBILIZATION
  • METABOLISM

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